The present invention relates to a stabilizer for asphalt emulsion, which can be used along with an emulsifier for emulsifying asphalt thereby improving the stationary stability and storage stability of the resulting asphalt emulsion.
Heretofore, asphalt has been used widely in paved roads, waterproof and adhesive materials, railroads, fuels, etc. However, asphalt has very high viscosity at ordinary temperatures and is thus very poor in workability. To secure desired workability at ordinary temperatures, therefore, there are cases where asphalt is used after its fluidity is improved by conversion into oil-in-water emulsion by use of a suitable emulsifier and water.
The known emulsifier for oil-in-water asphalt emulsion includes an anionic emulsifier, a cationic emulsifier, an amphoteric emulsifier and a nonionic emulsifier, and used depending on the intended use. Among these, the nonionic emulsifier is excellent in chemical stability. That is, the nonionic emulsifier neither forms insoluble salts nor is separated upon contamination with polyvalent metal ions or other impurities contained in asphalt or water or from the outside of the system. Accordingly, if chemical stability is necessary for asphalt emulsion, the nonionic emulsifier is used preferably.
As the nonionic emulsifier, polyoxyethylene alkyl phenyl ethers such as polyoxyethylene nonyl phenyl ether and polyoxyethylene octyl phenyl ether, and polyoxyethylene alkyl ethers, are generally used.
In the technology concerned with asphalt emulsion using a nonionic emulsifier, there is known asphalt emulsion for O/W prime coating using asphalt, a hydrocarbon- or halogenated hydrocarbon-based organic solvent, a cationic emulsifier, a nonionic surfactant having ethylene oxide added to fatty alcohol or alkyl phenol, and water (JP-A 56-8462). Further, an oil-in-water asphalt emulsion using an ethylene oxide-propylene oxide-ethylene oxide block polymer adduct having a C8-22 alkyl or alkenyl group (JP-A 11-116816) is known. Further, an oil-in-water emulsion using a nonionic emulsifier having an aryl group or an alkyl aryl group and a polyoxyethylene group or a nonionic emulsifier based on an ethylene oxide-propylene oxide-ethylene oxide block polymer adduct (JP-B 47-35059) is known. In addition, a C10-22 alcohol-ethylene oxide adduct (U.S. Pat. No. 3,740,344) is known as a nonionic emulsifier for regulating the curing time of an anionic emulsifier. Further, use of an ethylene oxide-propylene oxide-ethylene oxide block polymer adduct as a surfactant for transporting asphalt emulsion through a low-temperature line (U.S. Pat. No. 5,156,652) is known.
However, these nonionic emulsifiers can satisfy chemical stabilization, but suffer from the problem that when asphalt emulsion to which such nonionic emulsifier was added is left for a long time e.g. a few weeks to several months, the emulsion becomes instable, and the stationary stability and storage stability of the asphalt emulsion are not satisfied at present.
The object of the present invention is to provide a stabilizer for asphalt emulsion, which has a good chemical stability and is excellent in the stationary stability and storage stability of asphalt emulsion, as well as an asphalt emulsion containing the same.
The co-inventors of the invention have found that a compound having a more average mole number of added oxyalkylene units than a conventional nonionic emulsifier provides an asphalt emulsion, emulsified with an emulsifier, with an improvement in a long stability.
The present invention relates to a stabilizer for asphalt emulsion, comprising a polyoxyethylene adduct compound having:
a terminal group R1 selected from a C8-22 straight-chain or branched alkyl group and a C8-22 straight-chain or branched alkenyl group,
a terminal group R2 selected from a hydrogen atom, a C1-4 straight-chain or branched alkyl group and a C1-22 straight-chain or branched acyl group, and
130 to 500 oxyethylene groups on the average for bonding the terminal groups R1 and R2 (the stabilizer is referred to hereinafter as stabilizer 1.).
Further, the present invention relates to a stabilizer for asphalt emulsion, comprising a polyoxyalkylene polymer with a weight average molecular weight of 12000 to 30000 containing oxyethylene groups and oxypropylene groups wherein the total molecular weight of the oxyethylene groups accounts for 75% or more of the total molecular weight of the oxyethylene groups and oxypropylene groups (the stabilizer is referred to hereinafter as stabilizer 2.).
Further, the present invention relates to an asphalt emulsifier composition comprising:
stabilizer (I) of the invention described above and
a nonionic emulsifier (II) comprising a polyoxyethylene adduct compound having:
a terminal group R3 selected from a C8-22 straight-chain or branched alkyl group and a C8-22 straight-chain or branched alkenyl group,
a terminal group R4 selected from a hydrogen atom, a C1-4 straight-chain or branched alkyl group and a C1-22 straight-chain or branched acyl group, and
50 to 100 oxyethylene groups on the average for bonding the terminal groups R3 and R4.
Further, the present invention relates to an oil-in-water asphalt emulsion comprising asphalt and the asphalt emulsifier composition of the invention described above.
Further, the present invention relates to roadway comprising asphalt and the asphalt emulsifier composition of the invention described above.
The invention provides use of the polyoxyethylene adduct compound (1) as defined above as a stabilizer for asphalt emulsion, use of the polyoxyalkylene polymer (2) as defined above as a stabilizer for asphalt emulsion, a method of stabilizing asphalt emulsion, comprising mixing it with the polyoxyethylene adduct compound (1) as defined above and a method of stabilizing asphalt emulsion, comprising mixing it with the polyoxyalkylene polymer (2). In the use and method, the above shown emulsifier (II) and a conventional emulsifier may be used.